This section provides background information related to the present disclosure, which is not necessarily prior art.
Motor vehicle heating, ventilation, and air cooling (HVAC) systems typically include an HVAC casing with an evaporator and a heater core housed therein. In a heating mode, airflow that has passed into the HVAC casing through the evaporator, which is often deactivated, is directed through the heater core by a temperature control door. In a cooling mode, the evaporator is activated and the temperature control door is positioned such that cooled airflow that has passed through the evaporator is directed around the heater core. A plurality of additional doors direct airflow out from within the casing to various areas within a passenger cabin of the motor vehicle. For example, a face outlet door controls airflow exiting the HVAC casing towards an upper portion of the passenger cabin and an occupant's face. A foot outlet door controls airflow exiting the HVAC casing towards a floor of the passenger cabin and an occupant's feet. Rear outlet doors control and direct airflow to a rear of the passenger cabin.
Motor vehicle HVAC systems also often include a windshield defrost mode and a side window demist mode. With typical HVAC systems, it is not possible to control side window demist operation independent of the windshield defrost operation, and to provide constant side window demist throughout different heating modes, such as foot and face heating modes, without including an excessive number of control doors. The present teachings address these issues by providing an automobile HVAC system that provides constant side window demist throughout various heating modes with a reduced number of control doors, which reduces costs, simplifies operation, and increases operational reliance of the HVAC system.